Combine the black beans, black-eyed peas, pinto beans, shoepeg corn, celery, cilantro, red and yellow bell peppers, green onion, pimento peppers, jalapeno pepper, and garlic in a large bowl. Set aside.
Bring the rice vinegar, olive oil, sugar, salt, and black pepper to a boil in a saucepan over medium-high heat until sugar is dissolved, about 5 minutes. All to cool to room temperature, then pour over the bean mixture. Cover and refrigerate for 2 hours or overnight. Drain before serving.